In a fuel cell system, reverse to the electrolysis of water, oxygen is electro-chemically reacted with hydrogen gas produced from hydrocarbon material in order to generate electricity and heat (warm water) during the chemical reaction.
The above fuel cell system uses oil-based fuel such as naphtha, kerosene and so on, or gas-based fuel such as city gas, etc. as the hydrocarbon material, and this hydrocarbon material is mixed with steam to produce gaseous fuel for reformed gas, and then this fuel for reformed gas is heated together with reforming catalyst, thereby hydrogen gas is produced.
Therefore, for the fuel cell system, the most important challenge is how to efficiently produce hydrogen gas from the hydrocarbon material, and various techniques have been disclosed for fuel reforming apparatuses and reformers which produce hydrogen gas.
For example, Patent document 1 discloses a technique for a fuel reforming apparatus in which a reformer and its associated devices are integrated as one unit. This fuel reforming apparatus comprises a vacuum thermally insulating chamber, and an inner space of the vacuum thermally insulating chamber is used as a flow channel of combustion gas in the reformer. The fuel reforming apparatus comprises a plurality of reforming tubes. The reforming tubes are arranged in parallel in the flow channel of the combustion gas and filled inside with reforming catalyst, and raw gas (fuel for reformed gas ) flows through the reforming tubes, thereby the raw gas is reformed.
By this technique, insulation can be provided by the vacuum thermally insulating chamber without using a heat insulating material such as ceramic fibers, etc. and it is therefore possible to reduce the size of the fuel reforming apparatus and improve thermal efficiency.
Furthermore, Patent document 2 discloses a technique for a single-tube cylindrical reformer which comprises a cylindrical reforming chamber provided with a preheating layer having a filler at a front stage of reforming catalyst layer, wherein exhaust gas flows along the inner side surface of the reforming chamber to heat the reforming chamber, and hydrogen gas produced in the reforming chamber flows along a flow channel formed in the outer side surface of the reforming chamber.
By this technique, since the preheating layer is provided, a pre-heater for material becomes unnecessary, raw material can be efficiently stirred, and the amount of heat consumption can be reduced. Moreover, the inner parts of passages, etc. are helically formed with, for example, blades, and the like, thereby uniform temperature distribution can be obtained, and it is possible to set outlet temperature at predetermined temperature by improving efficiency of heat recovery.
Patent document 1: Japanese Patent Publication Laid-open No. 2003-327405 (claims 1, 2, 3 and 4, FIG. 1)
Patent document 2: Japanese Patent Publication Laid-open No. 2002-187705 (claim 1, FIG. 1)